1. Field of the Invention
The present invention relates to a boresighting apparatus and more particularly to a boresighting apparatus for boresighting a laser with a forward looking infrared device (FLIR) having a fluorescent conversion material.
2. Background Information
The use of both passive and active electro-optic sensors which employ lasers as an illumination source has become widespread in both the commercial and military markets. In military systems, for example, imaging infrared sensors have often been used for target acquisition, followed by a rapid and precise illumination of the target with a laser for measuring range to a target, designating the target for a laser guided bomb or for further information gathering. To achieve high precision, weapons must be accurately boresighted to (i.e., aligned with) sensors, using such a system as that described in U.S. Pat. No. 5,838,014, the disclosure of which is hereby incorporated by reference in its entirety.
However, conventional boresighting methods are susceptible to damaging problems which can hamper system performance. These methods generally fall into two categories: 1) having a dedicated laser detector in the boresight module or 2) using a thermal conversion material that absorbs the laser radiation, heats up, and then thermally emits radiation that can be detected by the passive sensor.
The first method is probably the most common and involves placing a detector in the boresight module that is mechanically aligned to the passive sensor boresight test pattern during assembly. This detector can be a single element detector, a multi-element detector such as a quadrant detector, or a position sensitive detector. In each case, a bias voltage is applied to each element, and readout/signal processing electronics must be provided. This additional electronics requirement increases the cost, size, and complexity of the boresight module and is an additional source for system failures. Use of a single element laser detector also involves the use of complex test pattern targets for location and alignment of the laser spot, further increasing the cost of the boresight module.
The second method of using thermal conversion materials to align Nd:YAG lasers (1.064 xcexcm wavelength) to long-wave infrared (LWIR) sensors operating in the 7-14 xcexcm waveband has always suffered from several problems. First, the thermal conversion materials usually do not provide a uniform spot for aligning the laser to the passive sensor. The laser power level and thermal conversion material heat sinking is closely matched so that heat is not conducted away too quickly for the alignment procedure to take place, but the heat cannot be allowed to build up to the extent that the thermal spot blurs and persists making boresight impossible. Another disadvantage is that the process of laser heating the thermal conversion material invariably causes damage to the material and therefore leads to a limited useful lifetime.
The ability to accurately align the pointing vectors of the laser and a passive sensor is important for the success of such a system. Accordingly, there is a need for a simple, inexpensive method of accurately boresighting a laser to a passive sensor (e.g., FLIR).
The present invention is directed to a system of boresighting a laser to a passive sensor using a fluorescent conversion material. Used in conjunction with a laser, such a material will not be damaged or result in a laser spot that grows in size with time. Also, problems associated with the mechanical alignment of a dedicated laser detector are avoided by the use of a fluorescent conversion material.
According to a first embodiment of the present invention, a boresighting system is provided comprising a laser emitting energy at a first wavelength, a boresight module having a fluorescent material, wherein the fluorescent material receives the emitted energy at a first wavelength and radiates the emitted energy at a second wavelength, and a sensor for detecting a location on the fluorescent material where the energy of a second wavelength is radiated.
According to a second embodiment of the present invention, a boresighting system is provided comprising means for emitting energy of a first wavelength, means for receiving the emitted energy, and means for identifying a location of the emitted energy on the receiving means using a fluorescent material to convert the energy of a first wavelength to energy of a second wavelength.
According to a third embodiment of the present invention, a method is provided for boresighting comprising the steps of aligning a sensor to a boresight module, emitting energy at a first wavelength from an energy source into the boresight module, absorbing energy at a first wavelength into a fluorescent conversion material located in the boresight module, radiating energy at a second wavelength from the fluorescent conversion material, detecting energy of the second wavelength at the sensor, and aligning the radiation source to the sensor based on the detected energy at the second wavelength.